the backbone is most likely to be affected in any bike accidents. i heard a doctor said lay down the patient on flat surface in such cases and make him keep the body straight. and ofc call some specialist.
You need to keep three main things in your mind before you head towards bike purchase
1- You should know specs
2- What you want to buy is being manufactured by whom?
3- What other organizations are offering this model or brand you want....
It depends on your specifications and descriptions. You need to go to some old shop or bikeshop and purchase there if available. It depends on age of your demanding device.